The invention relates to a lock-key system including a flat key which is insertable in the keyway of a cylinder core, wherein grooves and ribs inside the keyway are assigned to ribs and grooves on both flat sides of the key, wherein the key is subdivided into different profile sections from the key spine to the key facing, with the section near the key spine configured as guide section and with the section near the key facing at least partially receiving the notches for the associated tumblers.
Designs for such flat keys or keyways are known in a wide variety. Examples include hereby EP 0 261 298 A2 or DE 43 04 604 C2.
Conventional lock cylinders with flat key and pin tumblers are “attacked”i.a. by “picking” with manual picking tools, picking guns or so-called electropick.
During picking procedure, the pin tumblers are brought into opening position by the suitable tool. By bracing the cylinder core in rotation direction, the tumblers are braced successively in opening position and held until all tumblers are open. This is implemented during manual picking quasi statically or dynamically when picking with the mechanical picking gun or the electropick are involved.
Various measures have been proposed to guard against unauthorized opening of lock cylinders with picking tools and—mostly in combination—used together. These measures involve. . .                particularly designed tumbler pins which interlock during “picking” with grooves or projections on the parting line between cylinder housing and cylinder core and prevent an “opening” by picking.        Particularly designed bores in cylinder core and/or cylinder housing for effecting during “picking” that the tumbler pins interlock therein and preventing an “opening”during picking as they do not reach without resistance the parting line between housing and core.        paracentric key profiles which inhibit the handling with picking tools.        
Although all described measures generally make picking more difficult, they are unable to prevent picking in principle.